Rotor blade with deicing means



July 8, 1958 R. H. PREWITT 2,842,214

ROTOR BLADE WITH DEICING MEANS Original Filed June 28, 1947 s Sheets-Sheet 1 INVENTOR Richard H. P/ewi ff ATTORNEY July 8, 1958 R. H. PREWlTT ROTOR BLADE WITH DEICING MEANS 3 Sheets-Sheet 2 Original Filed June 28, 1947 ATTORNEY July 8, 1958 R. H. PREWITT 2,342,214

ROTOR BLADE WITH DEICING MEANS Original Filed June 28, 1947 3 Sheets-Sheet 3 INVENTOR Richard H. Prewiff 52m A l n ATTORNEY this invention. "saved, .both at the inboard connection and throughout the blade. The latter weight saving is accomplished due 'to thelfact that proper chordwise balance can be accomf pli'shed without the use of nose weights which do not con- 2,342,214 I RGTOR BLADE WITH DEICING MEANS "Richard-H. Prewitt, Wallingford, Pa.

vOriginal application -.lune 28, 1947; Serial No. 724,836,

now Patent No. 2,638,170, dated May 12, 1953. Di- 1 .vided and this application May 7,1953, Serial No.

6 Claims. (Cl. 170-1354) This invention relates to'aircraft propellers or rotors,

States Patent and is more particularly concerned with features of blade. 1

construction, as fully described hereinafter. This application constitutes a division of application Ser. No.

724, 83.6,"'filed lune 28, 1947, now matured into Patent No. 2,638,170, of May 12, 1953.

In'the past'considerable difficulty has been experienced with blade failures occurring at the inboard end between the blade proper and the structurenear the hub to which the blade is attached. These difiiculties have been brought about as a result of fatigue risers occurring at abrupt section changes, as where pins or rivets or flanges are used totransfer the load fromthe blade proper to the .inboard'attaching structure. In order to avoid structural failures the'weight of the blade attaching structure becomes excessive where existing fatigue risers are present.

The method of transforming from a round husky struc- I g jtural member (suitable for mating a machined part) to the main structural assembly of the blade proper, as taught in'this invention, advances the art of rotor blade fabrication tremendously since many fatal accidents may be avoided due to the obviously better control over in-- spection. and assembly of the simple parts disclosed in In addition, considerable weight can be tribute to'the blade strength yet require a part of the remaining blade strength to carry'the centrifugal and inertia forces that they exert on the hub.

"It is among the objects of the invention; to provide a blade with a conduit for conducting hot gases under the control of thermostatic means and .to provide, ablade 'wi th'a conduit for conducting hot gases with a valve con- "trolling exhaust of gases from the COnduit QpositiOned :between closed andzo'pen according to the sense of the difierential between aerodynamic pressures external of "the blade and gas pressures in said conduit.

,"Figure 1 shows a perspective view of a propeller or 'rotor'blade. Figure 2 shows a partially completedelevation perspective view of a helicopter, incorporating. the features of this invention. 'Figure 3 shows a cutaway perspective view of the internal end of the blade shown 'in Figure '1. Figure 4 shows a cross section of the stiffening members shown in Figure 3;- and Figure 5 isanalternate modified construction ofthe trailing edge structure shown in Figure 3.

'The blade construction taught in this invention involves the forming of a tubular member 2 into a nose I airfoil shaped member 3 which maintains the external contour of the blade in its forward section. The tube is preferably a single integral tube formed by drawing operations 'into a plurality of portions having respectively diflierent sectional profiles, one of which, at the root, is cylindrical or annular, and another of which is as of an airfoil nose section terminating toward the trailing edge of theblade,

edge of' the blade,

2,842,214 Patented July 8, 1958 ice 2 preferably in a generally flatvertical wall 3. A thin sheet 4 of metal such, illustratively, as of stainless steel is completely wrapped around the formed nosemember '3 and attached thereto by suitable adhesive. The stain lesssteel sheet '4 may extend to the trailing edge 5, or to any position short of the trailing edge, provided suitable supporting structure is used to maintain and supportthe external contour of the blade.

An-external telescoping collar 6 is fitted over the inboard end of the tubular member 2 and suitably attached such 'asby welding, as shown, or other suitable means.

The function of this collar is to transmit the centrifugal loadsfrom the'blade to its inboardconnection, such as shown at 7, Figure 2. At the outboard end of blade 1, weight8 is attached to formed spar tube 3 at. pivot 9.

Adjusting screw'ltl is adjusted through bushing 11, which forms a part of nose airfoil shaped member. 3. The-center "oftgravity 12 of weight 8 lies slightly aft of a theoretical line passing between the axis of rotation of the rotor 13, Figure 2, and pivot 9 so that in operation a continual force is exerted on weight 8, tending to move it forward against adjusting screw 10. Thus, when the adjusting screw 10 is turned in a tightening sense, the weight is forced aft, and when the adjustingscrew is turned in a loosening sense, the weight is permitted to move forward with the aid of centrifugal force acting upon'itf around itspivot'9. The tip of the blade is made oftwe formed members 14, suitably matedand attached I to main cover 4 and nose airfoilshaped member 3 with screws to permit changing'the' size oftheweight member '8 to account for variation in the longitudinal balanceof [the blade '1, resultingfrom manufacturingweight deviations. Adjustable weight member 3 is used to obtain proper .chordwise center of gravity for blade 1. The.

'effectivenessof moving a small weight fore and aft near the tip ofthe blade is great, relative tofore and aft movement of similarv weights located near the axis of rotation 13, Figure 2.

Atithe inboard end of the blade manifold15 receives andtransmits hot gases from a suitable source-through flexible tubing 55, (Figure 2) attached at 16, and directs the hot gases into the aft inboard section of the blade at from which the gases are sucked through holes 1'8 lying along the neutral axis of the nose airfoil shaped member. The centrifugal force acting on the column'o'f hot gases within the nose airfoil shaped member 3 creates.

a suction which draws 'thehot. gascs=through the leading and out automatically-adjusted vent 20 located at or near the tip of the blade. In an alternate construction the manifold 15 and holes 18 maybe eliminated, "and the hot gases may pass directly through'the tube member 2 and the nose airfoil shaped member 3.

Experience has shown that the. inboard end of the blade 'is s'ubje'ctto more than-ordinary punishment due to the bendingmoments in the plane of rotation, resulting from blade dampers; or, in'the case of rigid rotors, from-the The blade of this invention .shows stiffening trailing'edge member 25; A '17 1s 1ncorporated in the blade either to provide means of'relieving stresses in the tubular member 2, or

for increasing the stiffness of the blade in the plane of rotation. Exit slot 20 may be arranged to. automatically 'close'when the deicing system is inoperative, and to automatically open for exhausting the spent hot gases when the deici ng system is operative. This is accomplished .by locating the hinged door, 62 comprising a hinge at 63, which under normal operating conditions will be the suction pressure on said column, when the door will,

close.

Figure 3 shows the inboard blade construction in more detail. The nose airfoil shaped member 3 may be seen in section at the upper end of Figure 3, and the cover 4 may be seen in more detail as shown by breakaway. In order to provide the most efficient blade it is necessary to reduce weight for payload considerations wherever possible, yet maintain structural integrity. It is well known in the art of blade design that additional strength is required at the inboard end of the blade, as Well as at other specific locations along the blade. The nose airfoil shaped member 3 constitutes the main structural member of the blade taught in this invention, and means have been established for varying the wall thickness of this member as necessary, such as shown at 28, where the wall thickness is decreased from a heavy wall at 26 to a thin wall at 27, through a gradual taper, to avoid stress concentrations. This changing of the wall thickness may be accomplished at any point along the blade, or it may be successively applied at several different points.

An enlargement of the reinforcing structural members 21, 22, 23, and 24, along with the reinforced structural trailing edge member 25, is shown in Figure 3. In addition, an automatic thermostat controlling unit 29 operates between trailing edge member 25 and the aft side of nose airfoil shaped member 3 to automatically adjust the fiow of hot gases internally of the nose airfoil shaped member 3, as required for deicing. Thus, for the system established, the hot deicing gases are permitted to flow through member 3 in cold weather, and are shut off automatically in hot weather. The structural member 24 is preferably constituted with a solid web to form a bulkhead or other chordwisely extending imperforate sheet or baffle to preclude the, outboard movement of the heated gases behind the leading edge forming spar tube 3. Such bulkhead can be formed anywhere along the length of the spar tube 3 provided it is outwardly of the holes 18 and inwardly of the outboard end of the spar tube 3 so as to permit centrifugal force to be effective to move the heated gases through the spar tube 3. The operation of the unit is as follows:

Arms 30 are fixed to plates 36 and pins 37 which register in loose holes in the aft face of the nose airfoil shaped member 3. Said pins, along with the Y arms 30 and plates 36 are free to move fore and aft except for the control of the aforementioned thermostat unit 29 in combination with the effect of the associated mechanism described below. It may be noted that a section 3 of the nose airfoil shaped member 3 is bored with one or more holes or series of holes 18 and that plate or plates 36 register adjacent holes 18.

The aft end of arms 30 are fixed to plunger 32 and collar 31 which carries flange 34 at its aft end. Stern 61 to which is fixedly attached collar 35 at its forward end forms a part of the case of the thermostat unit 29. Spring 33 is interposed between movable flange 34 and fixed collar 35 so as to continually exert a force tending to return plunger 32 and assembly flange 34, collar 31, Y members 30, guide pins 37 and plates 36 aft creating a greater gap between the forward faces of said plates and the aft face of nose airfoil shaped member 3.

Thermostat unit 29 is supported to trailing edge structure 25 through resilient member 60. The thermostatic unit is arranged to respond to the temperatures of the 'or as a resultant of both, according to desire.

gases, or to the temperature of the exterior of the blade, Thus, with increased temperature thermostat unit 29 expands tending to close the aperture between the aft areas 19 of the blade and internally of the nose airfoil shaped member 3. Additional expansion of thermostat 29 after plates 36 register against aft face of nose airfoil shaped member 3 is taken in resilient member 60. With plates 36 registered as described, the fiow of air from chamber 19 to internally of member 3 is cut off.

When thermostat 29 is cooled it contracts, permitting spring 33 to force the plunger 32 into thermostat 29 and move assembly of ring 34, collar 31, Y members 30, guide pins 37, and plates 36 aft, opening a space between said plates and the aft faces of apertures 18, thus permitting the flow of hot air into the nose section 3 of the blade. Centrifugal forces acting on the column of air or gaseswithin the nose airfoil shaped member 3 acts as a suction pump to maintain a suitable flow of the deicing gases.

The aft section of the stainless steel cover is supported by a preformed metal structure, and a trailing edge member, shown in Figure 3. The exact nature of this structure and of the trailing edge may be varied to fit the circumstances involved in the specific blade under consideration.- However, tests have indicated that the structure shown has certain specific advantages and that it is adequate.

It may be noted that the lower chord support structure 38 and upper chord support structure 44 are of continuous design from the structural member 24 to the tip of the blade. The design incorporates a blanked and formed continuous member 38, having lightening holes 39, semi-circular stiffening members 40 between substantial flats in a general omega section, shown in detail in Figure 4, skin support projections 41 and shear tabs 42. The aft end of the chord formed members 38 and 44 have projections 43 which overlap a trailing edge member 45. This trailing edge member may be either made from a solid piece of light material such as wood, bakelite or other resins, or from a piece of formed metal, preferably of hollow construction. A further modification of this structure is shown in Figure 5.

In this modified form of the trailing edge structure chord member 64 (corresponding to member 38 of Figure 3) extends to a point 65 near the trailing edge and chord member 66 (corresponding to member 44 of Figure3) is bent at 67 into a U shape, permitting a mating of chord member 66 with chord member 64 at 68 where the two chord members are securely connected by suitable adhesives. i

It is contemplated to attach chord members 38 and 44 to external skin 4 and to formed nose member 3 and to trailing edge member 45 through suitable adhesive, preferably a thermo-setting material such as Cycleweld. It is further intended to accomplish this adhesion by the use of external molds and internal pressure through a suitable rubber bag or container for transmitting the internal pressure to the chord members 38 and 44 so as to maintain suitable contact during the curing of the adhesive involved. By the use of an external mold, the external shape of each blade should be identical, providing improved performance.

Figure 2 shows several applications for the blade taught herein. For example, blades of the tail propeller or rotor 46 may utilize the construction taught herein, or blades 1 and/or 47 may utilize it. In more detail Figure 2 is shown as an incomplete example of a helicopter showing landing gear wheels 48, body 49, powerplant 50, rotor drive 51, manifold 52, heat exchanger 53, hot air duct 54, and individual blade hot air ducts 55. It is proposed to utilize the heat from the exhaust system of the powerplant 50 through heat exchanger 53 to provide the hot air through duct 54 at stationary disk 56 into the chamber internally of the rotating manifold collector 52 which supplies hot air to the blades hereinbefore described, through ducting 55. It may be noted that blade 1 is attached to hub 57 through vertical hinge 58 and horizontal hinge 59. Blade 1 is commonly known as a flapping type blade, and therefore it is desired that duct 55 be of flexible construction, attaching to apertures 16 of manifold shown on Figure 1. However, in the case of the rigidly attached blade 47 it may be easier to eliminate the flexible manifold 55, and make this member more rigid. Likewise it may be desirable to conduct the gases directly through the inboard members of the blade, such as through the structural member 57 or blade 47, or through the members 57, 59, 58 and 7 to blade 1.

Engine controls and rotor controls, transmissions, clutches, seats, and the like, being so firmly established in the art, are not specifically shown and described herein. However, this invention contemplates the use of a blade in a propeller or rotor on a machine incorporating all of the devices necessary for successful flight. For example, no power connection is shown between the powerplant 50 and the tail propeller or rotor 46. Yet such connections are old in the art, and standard methods of power transmission controls, etc. are firmly established and are anticipated herein.

While a heat exchanger is shown for the source of heat, it is contemplated that other sources of heat may be utilized for providing the energy for blade deicing, such as a separate small heater unit incorporated in the inboard end of the blade, or on the hub, or in the body of the machine.

Having described my invention, I claim: I

1. In an airfoil, a blade incorporating a hollow tubular member therein having an airfoil nose contour, means for leading hot gases into the inboard end of said blade external of said tubular member, thermostatic means disposed at the inboard end of said blade and controlling the passage of hot gases from saidblade into said tubular member, and means at the outboard end of said blade responsive to the spanwise pressure flow of gases centrifugally induced in said tubular member for permitting the said hot gases to escape from said tubular member and I out of said blade near the external tip of said blade.

2. In a blade, means for conducting hot gases into the blade, a hollow tubular member extending internally of said blade from one end to the other end, and automatically operable thermostatic means located in the region of hot gas entry into said blade to control the passage of hot gases from said blade into said tubular member.

3. In a blade, means for deicing same comprising a tubular member having a plurality of apertures leading aft into the interior of the blade, means for introducing hot gases into the blade generally adjacent to said apertures, a valve organization including a plate movable between blocking said apertures and opening said apertures to permit hot gases in the blade to enter said tubular member, a thermostatic control engaging said plate and forcing same to block said apertures when the temperatures in cident on the control are relatively high to preclude deic- 6 ing flow through said tubular member and a resilient mount for said thermostatic control means to absorb excess forces between the thermostatic uint and said plate. 4. In a blade, means for conducting hot gases internally 'of said blade from the inboard end to the outboard end thereof, a hinged member mounted on the blade the outer surface of which is part of the outer surface of the blade and is exposed to the aerodynamic forces on the external surface of the blade, the inner surface of said member being in communication with said means at said outboard end and exposed to internal forces thereon from centrifugal forces on said gases, said member being substantially free of mechanical bias and movable in and out of surface continuity with said blade in accordance with preponderance of externalor of internal forces thereon, and means defining a discharge for said gases when the internal forces preponderate over the external forces on said member.

5. In a blade, an external cover, a hinged closure in the cover in a region of and being exposed externally to relatively high aerodynamic pressures externally of the blade during blade movements, means providing spanwise gas flow through the blade accelerated under centrifugal force to impose internalgas pressures on said closure, thermostatic control means disposed inboardly of the blade with relation to said closure operative on said means in one sense to cut off the spanwise gas flow to establish preponderance of the aerodynamic forces to move the closure closed and operative in another sense to permit spanwise gas flow to establish preponderance'of the internal pressure to move the closure open to exhaust said gas flow.

6. In a blade, means for conducting hot gases internally of said blade from the direction of the inboard end toward the direction of the outboard end of said blade, a movable exit device for exhausting said gases comprising a movable element forming in one attitude a continuation of the surface of said blade, said element internally being exposed to the internal pressure of said means for con ducting, said element movable in response to the differential between internal and external pressures and controlling an exhaust slot in accordance with its positioning between closed and open and its position being automatically controlled as a function solely of a differential between the internal and external pressures incident thereon, and thermostatic means generally in the inboard end of said blade for controlling the flow of hot gases into said means for conducting.

References Cited in the file of this patent UNITED STATES PATENTS 1,420,619 Barton June 27, 1922 1,783,590 Simon Dec. 2, 1930 1,876,620 Crossland Sept. 13, 1932 1,957,413 Price May 1, 1934 2,469,480 Sikorsky May 10, 1949 FOREIGN PATENTS 589,059 Germany Dec. 21, 1926 

